The use of chemical warfare agents continues to be a viable threat to civilian populations as well as to military installations. Such chemical warfare agents possess toxic properties capable of killing, injuring or incapacitating people. It has been estimated that 25-27 nations possess chemical weapons, which are often referred to as the “poor man's nuclear weapon.” The manufacture of chemical warfare agents in small quantities by terrorists is an ongoing threat, and the manufacture and use of military quantities of chemical warfare agents for delivery against U.S. troops is always a potential.
Therefore, effective countermeasures are needed to maintain adequate security and protection of population and military centers. Such countermeasures broadly include defense against chemical weapons and accurate means of detecting chemical agents. One type of a chemical agent detector means is a point detector capable of providing quick warning to those nearby that a chemical attack has occurred.
Chemical agents are colorless and sometimes odorless, which at very low concentrations, can cause incapacitation or more serious effects on people. Chemical warfare agents delivered to a target site may be in the form of a gas or vapor at room temperature that can affect the target through the lungs, skin and clothing, and are usually classified as nonpersistent since they lose effectiveness after a few minutes or hours.
Other chemical warfare agents that are classified as persistent have a relatively high boiling point, and a relatively low vapor pressure. They are typically delivered to the target site in droplet forms, and can exhibit varying size droplet particles ranging from 100 microns to 5000 microns, depending on the delivery system used. The aerosolized delivery of such chemical warfare agents can be achieved even by low-tech aerosolization methods including agricultural crop-dusters, aerosol generators, backpack sprayers, or hand-size atomizers. Due to the properties of such agents, they tend to remain in the environment as a liquid for as long as a week. Thus, detection of such chemical warfare agents must be made at the earliest possible time to reduce the number of potential persons affected. Often, this is best facilitated through the detection of the agent in the droplet or aerosol form during the delivery phase.
Chemical vapor detection systems make up a class of point detectors that are reliable and effective in a range of testing conditions. They generally employ spectrometric techniques to identify compounds based on the unique spectral profile generated. The chemical vapor detection system separates and identifies each component of a molecule based on relative speeds of travel in an electric field.
The chemical vapor detection systems are efficient, relatively accurate and require no consumable testing materials or reagents. They can be used for continuous real time point sampling operations with minimal labor and maintenance requirements. Such systems can be left unattended in an area to monitor general air quality, or used to detect dangerous chemicals spreading in an area. Using such systems, chemical warfare agents in the form of vapors or gases can readily be detected, however, the same systems provide limited aerosol detection.
Liquid surface samplers can provide for aerosol detection if adequate aerosol deposition occurs on the tested surfaces. Such chemical detection systems are equipped to detect chemical agents in droplet or aerosol form, and operate by contact of the chemical agent to a detector plate in amounts sufficient to reach a saturation point. The detector plate includes a conducting circuit containing a chemically reactive conducting matrix. Once the agent comes in contact with the conducting matrix, the conducting matrix undergoes chemical changes, which activates the conducting circuit.
Such liquid surface sampling systems are less sensitive to chemical agents with very small droplet or aerosol particle sizes. Furthermore, such systems require regular replacement of the detector plate and maintenance, and depend on optimal testing conditions, while exhibiting slower reaction times and lower threshold of sensitivity than spectrometric methods.
Accordingly, there is a need for a device attachable to a chemical vapor detection system that can enhance its capability to monitor and detect droplet or aerosol forms of chemical warfare agents while enhancing the detection of vapor chemical agents, thus enabling detection of both vapor and droplet forms of chemical warfare agents over a range of temperatures and testing conditions in a simple, reliable and cost effective manner.